ben-manes commented on code in PR #4551:
URL: https://github.com/apache/accumulo/pull/4551#discussion_r1597494565
##########
server/tserver/src/main/java/org/apache/accumulo/tserver/ScanServer.java:
##########
@@ -246,9 +246,30 @@ public ScanServer(ScanServerOpts opts, String[] args) {
LOG.warn(
"Tablet metadata caching less than one minute, may cause excessive
scans on metadata table.");
}
- tabletMetadataCache =
- Caffeine.newBuilder().expireAfterWrite(cacheExpiration,
TimeUnit.MILLISECONDS)
-
.scheduler(Scheduler.systemScheduler()).recordStats().build(tabletMetadataLoader);
+
+ // Get the cache refresh percentage property
+ // Value must be less than 100% as 100 or over would effectively disable
it
+ double cacheRefreshPercentage =
+
getConfiguration().getFraction(Property.SSERV_CACHED_TABLET_METADATA_REFRESH_PERCENT);
+ Preconditions.checkArgument(cacheRefreshPercentage < cacheExpiration,
+ "Tablet metadata cache refresh percentage is '%s' but must be less
than 1",
+ cacheRefreshPercentage);
+
+ var builder = Caffeine.newBuilder().expireAfterWrite(cacheExpiration,
TimeUnit.MILLISECONDS)
+ .scheduler(Scheduler.systemScheduler()).recordStats();
+ if (cacheRefreshPercentage > 0) {
+ // Compute the refresh time as a percentage of the expiration time
+ // Cache hits after this time, but before expiration, will trigger a
background
+ // non-blocking refresh of the entry so future cache hits get an
updated entry
+ // without having to block for a refresh
+ long cacheRefresh = (long) (cacheExpiration * cacheRefreshPercentage);
+ LOG.debug("Tablet metadata refresh percentage set to {}, refresh time
set to {} ms",
+ cacheRefreshPercentage, cacheRefresh);
+ builder.refreshAfterWrite(cacheRefresh, TimeUnit.MILLISECONDS);
Review Comment:
> If these will not go to slf4j then we may want to have these background
refresh task try/catch/log into a slf4j logger we know about.
By default the platform logger redirects to `java.util.logging` (jul), which
if not configured would go to the console. You can redirect the platform logger
using `slf4j-jdk-platform-logging`, jul (with small overhead) using
`jul-to-slf4j`, and console using
[sysout-over-slf4j](https://projects.lidalia.org.uk/sysout-over-slf4j/quickstart.html).
It is usually good to configure the redirects in an application to ensure
everything goes to your preferred logger (log4j2).
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